1. Field of the Invention
The invention relates to a method and apparatus for aligning a selected object with respect to the top-dead-center of a circular wheel. More particularly, the invention relates to an apparatus useful for aligning an extrusion nozzle with respect to the top-dead-center portion of a chilled casting wheel.
2. Description of the Prior Art
In the production of glassy alloy continuous filaments, an appropriate molten alloy is typically quenched at extreme quench rates, usually at least about 10.sup.4 .degree. C. per second by extruding the molten alloy from a pressurized reservoir through an extrusion nozzle onto a high speed rotating quench surface, as is representatively shown in U.S. Pat. No. 4,142,571 for "Continuous Casting Method for Metallic Strips" issued Mar. 6, 1978 to M. Narasimhan, hereby incorporated by reference. Such filaments are necessarily thin, typically about 25 to 100 microns, owing to the extreme heat transfer rates required to prevent substantial crystallization, though considerable selectivity may be exercised respecting the transverse dimensions and cross section of the filament. The quench surface is often provided by an annular outer peripheral surface of a vertically disposed wheel which has its rotational axis disposed substantially horizontal.
To obtain filaments of uniform cross section and uniform mechanical properties, it is necessary to align the nozzle substantially parallel to the wheel rotational axis. If the nozzle is twisted with respect to the wheel axis, extruded molten metal will not contact the chill quench surface uniformly across the width of the surface. The resultant difference in quench rates will cause variations in the properties of the cast material.
The process of aligning the extrusion nozzle over the wheel top-dead-center is generally quite cumbersome because the extrusion apparatus is located over the wheel. As a result, it is not possible to sight directly down to the top of the wheel. In ordinary alignment procedures, an experienced technician uses a ruled scale to estimate the nozzle alignment. This is necessarily inaccurate and depends on the individual judgment and experience of the technician. Consequently, there remains a need for a convenient, easy to use and consistently accurate device for aligning extrusion nozzles with respect to the top-dead-center of a high speed rotating casting wheel.